The present invention relates to a portable telephone apparatus that controls wireless communication through a base station installed in a mobile phone system.
In recent years mobile phone infrastructure has been developed in industrialized nations such as Japan, the US and European countries, as well as various other countries around the world.
Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), and Code Division Multiple Access (CDMA) are examples of systems generally used in wireless communication. CDMA is thought to have potential as it has superior multipath phasing measures and allows better communication in built up areas.
The CDMA mobile phone system was developed by the US company Qualcomm. After being adopted as US standard IS95 in 1993, the system came into mainstream use and is now employed in numerous countries including Hong Kong (since September 1995) and South Korea (since January 1996). Meanwhile, the IS95 standard was revised to IS95A and then to IS95B. Japan employs a mobile phone system ARIB STD-T53 (commonly known as T53) that conforms with IS95A.
As mobile phone system infrastructure is improved in various countries, the appearance of portable telephones that are capable of international roaming is anticipated.
A portable telephone apparatus capable of international roaming can be used in a first country, and, when taken from the first country to a second country, can also be operated in the second country. Here, it is possible that a portable telephone apparatus compatible with the US IS95 system could also be used in Hong Kong and South Korea, and thus so-called international roaming could be performed between the US and Hong Kong and the US and South Korea. This is because Hong Kong and South Korea use the same IS95 system as the US, meaning that providing a portable telephone apparatus performs processes compatible with IS95, communication can take place with the mobile phone system in any of these countries.
However, in such international roaming, when a portable telephone apparatus is taken to a second country, there are cases in which the user of the portable telephone apparatus desires to be warned prior to use in the second country. That is to say, when the operation of types of communication services such as call charge billing, e-mail and the Internet is different between the first and second countries, it is desirable to have some way to notify the user that the country has changed and have the user carry out the appropriate settings for use in the second country. However, conventional portable telephone apparatuses have no mechanism for recognizing which country they are in, and so are unable to warn the user that changing of settings is necessary.
The object of the present invention is to provide a portable telephone apparatus that can recognize which country it is located in, and prompt the user to perform the appropriate operations for use in that country.
The portable telephone apparatus of the present invention as explained above includes: a country information storage unit having a plurality of pieces of country information for a plurality of countries, each piece of country information corresponding to a time difference for each of the plurality of countries with reference to a predetermined time zone; a reception unit for receiving a message generated by a base station; a reading unit for reading from the received message a local offset showing a time difference for an area in which the base station is located; and a display unit for retrieving a piece of country information corresponding to a time difference closest to the read local offset from the country information storage unit, and displaying the retrieved one.
With the stated construction the user can make the necessary settings for use in a second country. If these settings are performed correctly it becomes possible to use the portable telephone apparatus in the second country even if various communication services such as call charge billing, e-mail and the Internet are different between the two countries. In this way international roaming is realized.
Here the portable telephone apparatus may include: a receiving unit for receiving, when two or more pieces of country information are displayed by the display unit, a selection operation from a user to select one; and the updating unit may update the piece of information stored in the operation country storage unit, with the one piece of country information selected by the operator.
With the stated construction a portable telephone apparatus requests the country of operation from the user when it is not possible to specify in which country of a plurality of countries on the same longitude the portable telephone apparatus is located. As a result, the accuracy of the country information displayed by the display means can be improved.